There has been known a shot-blasting apparatus configured to project shots onto a workpiece disposed in a projection chamber to process a workpiece (see the following Patent Document 1). In the shot-blasting apparatus, due to collision of shots against the workpiece in the projection chamber, a large amount of powder dust is inevitably generated in the projection chamber. Therefore, such powder dust generated in the projection chamber is collected by a dust collector to thereby keep a working environment around the apparatus clean.
As an example of the shot-blasting apparatus, a type shown in FIGS. 1 and 2 is commonly known. This type of shot-blasting apparatus comprises a cabinet 1, and a rotary hanger 2 installed inside the cabinet 1. The rotary hanger 2 is equipped with a hanger hook for suspendingly supporting a workpieces.
The rotary hanger 2 is a member which has a drum shape (cylindrical shape) and comprises two process chambers 3a, 3b arranged at radially opposed positions, wherein the hanger hook is configured to suspend a workpiece in each of the process chambers. The rotary hanger 2 is configured to be rotatable intermittently about a longitudinal axis extending in a vertical direction, as indicated by the arrowed lines R1.
According to this rotation, each of the process chambers 3a, 3b is selectively moved between a carry-in-and-out position on the side of a front end of the apparatus and a projection position on the side of a back end of the apparatus. Each of the process chambers serves as a carry-in-and-out chamber 3a for carrying in and out the workpiece at the carry-in-and-out position and as a projection chamber 3b for projecting shots to the workpiece at the projection position.
In this type of shot-blasting apparatus, after placing a new workpiece on the hanger hook in the carry-in-and-out chamber 3a, the rotary hanger 2 is rotated 180 degrees to allow the carry-in-and-out chamber 3a having the workpiece disposed therein to be located on the side of the back end of the apparatus so as to serve as the projection chamber 3b. Then, a projector is activated to project shots onto the workpiece suspended in the projection chamber 3b. 
In this type of shot-blasting apparatus, a cabinet suction port 4 is provided in a back-end region of the cabinet 1 at a position on the side of one lateral edge of a top wall of the cabinet 1, to introduce external air into the cabinet 1 through the cabinet suction port 4. Further, a separator suction port 6 is provided in a separator 5 disposed at a widthwise center of the back-end region of the cabinet 1, to suck external air therethrough. The external air introduced from the cabinet suction port 4 and the separator suction port 6 flows into a dust collector (not shown) via ducts 7, 8.
The above conventional shot-blasting apparatus is thus configured to remove powder dust from air in the projection chamber 3b by the dust collector having a suction device.